I have a problem with my exported videos, and it's that my videos would get "pulses" of blurs towards the end. It's not blur like "smoothly blended frames" way, but more of a "pixelated low quality" kind of way. The video would blur/pixelate, and then gradually gets clear and then blur/pixelate, and gradually gets clear and repeats. I did not use any filters or effects at all, but the video somehow always screw up towards the end.

I have a high definition youtube video to explain it. Watch on HD and fullscreen and skip to around 4:20 to see what I'm talking about.
http://www.youtube.com/watch?v=XTE6gPrxzJ4

The blur is not because of youtube since the same thing happens on the original exported file. Also I've checked my original unedited footage, and they're all crystal clear, so the fault is at the encoding.